This invention relates generally to magnetic or magneto-optical recording systems for digital information, and more specifically to such a system capable of driving a magnetic transducer with a current higher than that due only to a power supply of a given voltage, in order to make possible the recording of high frequency digital signals.
Magnetic transducers are inductive, so that they offer high impedances when recording high frequency digital information. Correspondingly high drive voltages are therefore required. It might be contemplated to provide inductance capacitance resonance networks in order to obtain sufficiently high voltages. This solution is unsatisfactory because it would be difficult to maintain LC resonance in cases where the information being recorded varies in a wide range of frequencies.
Another solution is found in Japanese Unexamined Patent Publication No. 3-276404. This prior art system (shown in FIG. 1 of the drawings attached hereto) teaches the connection of a pair of inductance elements between a direct current power supply and the respective extremities of a transducer coil. Two switches are alternately turned on and off to cause the transducer to be excited from the power supply via one of the inductance elements and then the other. Energy is stored on one of the inductance elements when the transducer is being excited via the other. Accordingly, when the transducer is subsequently excited via said one inductance element, the energy that has been stored thereon is also utilized to energize the transducer. A net current flowing through the transducer is therefore of greater magnitude than the current offered solely by the power supply.
This prior art transducer drive system is objectionable as the semiconductor switches usually take the form of metal oxide semiconductor field effect transistors. Such switches permit the flow therethrough of a current of varying magnitudes when off. Consequently, the current flowing through the transducer has so far been not constant. The prior art system has thus necessitated a waste of power, as will be later discussed in more detail.